1. Field of the Invention
The present invention relates to a method of making or producing a thin film magnetic head in general employed in a recording medium drive or storage device such as a magnetic disk drive and a magnetic tape drive, and in particular, to a method of producing a thin film magnetic head including a magnetic core piece and a coil girdling around the magnetic core piece.
2. Description of the Prior Art
A thin film magnetic head in general includes an insulating layer incorporating a thin film coil pattern. It is preferable that the insulating layer is flattened at the exposed surface thereof before another thin film coil pattern or an upper magnetic or pole layer is formed on the exposed surface of the insulating layer. The flat surface of the insulating layer is expected to realize establishment of another thin film coil pattern or the upper magnetic layer of a fine accurate pattern over the insulating layer. Such a fine accurate pattern contributes to reduction in the width of a recording track on a magnetic recording medium, for example.
In the case where the insulating layer is subjected to a flattening grinding treatment, the insulating layer is in general made of a metal oxide such as Al2O3. Sputtering or vacuum evaporation is employed to form a layer or lamination of such a metal oxide.
A still higher rate for writing binary magnetic data is expected in the technical field of magnetic disk drives. For example, a smaller coil having a reduced or narrower gap between the adjacent conductive lines is supposed to lead to accomplishment of the still higher rate for writing in the thin film magnetic head. If the gap between the adjacent conductive lines is reduced in this manner, it is impossible to employ a conventional method, such as sputtering and vacuum evaporation, for filling out the narrower gap between the adjacent conductive lines. Sputtering and vacuum evaporation cannot avoid generation of voids within the gap between the adjacent conductive lines. The remaining voids may induce corrosion or oxidation of the conductive lines, which may result in an increase in electric resistance of the conductive lines. An electric current of a higher voltage should be supplied to such a coil after corrosion or oxidation. The coil may also suffer from an accelerated generation of heat. These are not preferable.
It is accordingly an object of the present invention to provide a method of producing a thin film magnetic head which includes a coil embedded in an insulating layer without any voids between adjacent conductive lines of the coil, keeping the surface of the insulating layer flat.
According to the present invention, there is provided a method of producing a thin film magnetic head, comprising: forming a magnetic core piece; forming parallel conductive lines, girdling around the magnetic core piece on a datum plane, so as to establish a coil; applying a liquid of a resist between the adjacent conductive lines in the coil; curing the liquid of the resist so as to form an insulating resin filler between the adjacent conductive lines; covering the insulating resin filler and the conductive lines with an insulating metallic layer; and subjecting the insulating metallic layer to a flattening grinding treatment until at least a part of the conductive line is exposed at a flattened surface.
The method of producing is allowed to employ the liquid of the resist, of a higher fluidity, to form an insulating material between the adjacent conductive lines in the coil. The liquid of the resist penetrates in every hole and corner between the adjacent conductive lines, so that the gap defined between the adjacent conductive lines is fully filled with the insulating material. No voids remain in the gap. The conductive line of the coil can be reliably prevented from corrosion or oxidation. Any fluid or liquid, such as a liquid of a thermosetting resin or a light-reactive resin, can be employed as the liquid of the resist. The light-reactive resin may include a resin reactive to irradiation of the ultraviolet and the like.
Moreover, the flattening grinding treatment can be conducted after the insulating metallic layer is formed to extend over the insulating resin filler in the method of producing. A relatively brittle or fragile insulating resin filler is reliably prevented from being subjected to the flattening grinding treatment. To the contrary, if the insulating resin filler is subjected to the flattening grinding treatment, the surface of the insulating resin filler gets sandy under the excessive influence of an abrasive agent, so that a flat surface cannot be obtained. According to the method of the invention, it is possible to reliably establish a flat surface on the insulating metallic layer after the flattening grinding treatment. A fine patterning can be achieved to form an upper coil and/or an upper magnetic layer on the flattened surface. Such a fine patterning is expected to contribute to reduction in the gap between the adjacent conductive lines in the coil and/or improvement in the density of recording tracks on a recording medium. A metallic oxide compound may be employed to form the insulating metallic layer, for example.
The method of producing preferably further comprises: applying the liquid of the resist until the conductive lines are fully sunk in the liquid of the resist; half-curing the liquid of the resist; and thereafter subjecting the liquid of the resist to a reactive etching process until a groove is formed between the adjacent conductive lines. If the aforementioned insulating metallic layer is formed to fill out the groove, the conductive line of the coil can be exposed during the flattening grinding treatment while the insulating metallic layer still remains between the adjacent conductive lines. The insulating metallic layer is allowed to reliably keep covering over the insulating resin filler even when the conductive line fully exposes its top surface. The insulating resin filler is reliably prevented from exposure during the flattening grinding treatment. Generation of a sandy surface can be avoided on the insulating resin filler.
An abrasive slurry preferably contains a reactive agent capable of changing its color in response to contact with the conductive line in the flattening grinding treatment. In general, a wafer is urged against the surface of a rotating faceplate in the flattening grinding treatment. An abrasive slurry is introduced to extend over the surface of the faceplate. The abrasive slurry serves to grind or polish the surface of the wafer. In this case, if the abrasive slurry contains the reactive agent in the aforementioned manner, the reactive agent serves to indicate the completion of the flattening grinding treatment. Specifically, an operator can reliably notice the exposure of the conductive line in response to the change of color during the flattening grinding treatment. The operator is allowed to reliably stop grinding upon the exposure of the conductive line. The insulating metallic layer is reliably prevented from an excessive removal during the flattening grinding treatment. The insulating resin filler is accordingly prevented from exposure after the completion of the flattening grinding treatment.
It should be noted that the insulating layer such as the insulating resin filler and the insulating metallic layer may be formed not only within the gap defined between the adjacent conductive lines of the coil in the aforementioned manner but also within the gap defined between a tip pole piece located outside the coil and the outer periphery of the coil as well as within the gap defined between the inner outline of the coil and the magnetic core piece.
The above-described method may contributed to production of a thin film magnetic head comprising: a magnetic core piece; a coil including parallel conductive lines girdling around the magnetic core piece over a predetermined datum plane; an insulating resin filler filled between the adjacent conductive lines; and an insulating metallic layer covering at least partly the insulating resin filler on the datum plane, said insulating metallic layer designed to define a flat top surface. Otherwise, a thin film magnetic head may comprise: a tip pole piece exposed at a medium-opposed surface; a coil girdling around over a predetermined datum plane and opposing its outer periphery to the tip pole piece; an insulating resin filler filled between the tip pole piece and the coil; and an insulating metallic layer covering at least partly the insulating resin filler on the datum plane, said insulating metallic layer designed to define a flat top surface. Furthermore, a thin film magnetic head may comprise: a magnetic core piece; a coil girdling around the magnetic piece over a predetermined datum plane; an insulating resin filler filled between the magnetic core piece and an inner outline of the coil; and an insulating metallic layer covering at least partly the insulating resin filler on the datum plane, said insulating metallic layer designed to define a flat top surface.